Organic electronic and optoelectronic materials have the attention of growing number of, particularly, physics and chemistry researchers for more than 50 years, the main mason of which is the higher possibility of modifying the chemical structures of the organic compounds. Thus, the properties of the materials could directly be affected. Until the mid-1980s, stability and performance of the devices made of organic materials fell short of those devices based on materials such as silicon or gallium arsenide. This has been changed with the appearance of a low voltage and efficient thin film light emitting diode. It provided the possibility of using organic thin films for a new generation of electronic and optoelectronic devices. It has now been proven that organic thin films are useful in various applications and organic light emitting device (OLED) is the most successful one, which is used now in full-color displays.
Generally, two groups of organic materials, small molecules and polymers, are used in electronic and optoelectronic devices and both can be processed from solutions and allow low cost fabrication of devices. Small molecule and polymer electro-luminescent devices are described, for example, C. W. Tang, Appl. Phys. Letters, 1987, 51, 913-915; J. H. Burroughes, Nature, 1990, 347, 539; U.S. Pat. No. 6,727,008, U.S. Pat. No. 7,133,032, WO 2007/134280A1; US2005/01184A1; WO90/13148; US005399502; U.S. Pat. No. 4,356,429.
Designing high performance optical and electronic organic devices requires understanding of their electronic structures, and even some small tunings in the structure or composition of an organic material can alter its original properties enormously. Modification of the structures of the conjugated organic materials to tune their optoelectronic properties is a challenging topic. Thiophene-based organic materials are among the most promising compounds with tunable functional properties by proper molecular engineering. For example, converting oligothophenes into the corresponding oligothiophene-S,S-dioxides has been shown to be useful for increasing both thin film photoluminescence efficiencies and molecular energy levels.
Recently, boron has been applied to alter the properties of organic electronic and optoelectronic materials, which gave interesting results. Presence of empty pz orbital of boron, which behaves as strong electron withdrawing atom when it makes three bonds, is the main reason for altering the properties. It delocalizes electrons strongly when it is integrated to “π” systems, and conjugated organoboranes are now considered as new class of organic materials with their widespread applications in electronics, optoelectronics and sensors.
Materials, having the combinations of different functional building blocks like thiophene, thiophene derivatives and boron, tend to emit bright white light from a single active molecular material (M. Mazzeo, Adv. Mater. 2005, 17, 34). The AIE (Aggregation-Induced Emission) nature and hole-transport capability of a material, comprised of tetraphenylethylene and triphenylamine, have enabled the fabrication of OLEDs devices with simple structures and low-cost but good performance (Tang Z. B. Adv. Mater. 2010, 22, 19). AIE-Active materials incorporated with an inherently electron-deficient group, dimesitylboryl, enable them to serve simultaneously as bifunctional materials of light emitter and electron transporting layer in OLEDs (Tang Z. B. Adv. Functional Mater. 2014, 24, 3611-3630). Thus, it would be desirable developing materials having thiophene, thiophene derivatives and boron to obtain various emissions for organic light emitting diodes.